Rosalina's Palpitations

I feel my heart race and thump in my
chest every once in a while. It lasts about half a minute. I feel dizzy and
get some chest pain and shortness of breath. Once I actually fainted when it
happened! This was very embarrassing as it occurred whilst I was in a
supermarket. They occur in random locations and there isn\'t a specific
trigger. The symptoms go when my heart stops racing. I avoid exercising in
case that sets it off. Do you think I should avoid exercising? I deny any
other symptoms.